Ozone water supply method and ozone water supply device

Abstract

An ozonated water supply method includes: feeding dissolving water contained in a circulation tank to an ozonation device at a given feed rate while feeding ultrapure water to the circulation tank, and returning ozonated water that has not been used at a use point to the circulation tank, dissolving ozone in the dissolving water using the ozonation device to obtain ozonated water, and feeding the ozonated water to the use point; feeding oxygen gas having a nitrogen gas content of 0.01 vol % or less to a discharge-type ozone gas-producer, and feeding the resulting ozone-containing gas to the ozonation device; adjusting the feed rate of the ultrapure water to the circulation tank; and adjusting the dissolved ozone concentration in the ozonated water. The method can reduce or suppress the accumulation of nitric acid in the recirculation system when a discharge-type ozone gas-producer is used as the ozone gas-producer.

The invention claimed is: 
     
       1. An ozonated water supply method comprising:
 feeding dissolving water contained in a circulation tank to an ozone gas dissolver at a given feed rate while feeding ultrapure water to the circulation tank, and returning ozonated water that has not been used at a use point to a position under the liquid surface in the circulation tank, dissolving ozone in the dissolving water using the ozone gas dissolver to obtain ozonated water, and feeding the ozonated water to the use point; 
 feeding oxygen gas having a nitrogen gas content of 0.01 vol % or less to a discharge-type ozone gas producer, producing ozone gas using the discharge-type ozone gas producer to obtain an ozone-containing gas, and feeding the ozone-containing gas to the ozone gas dissolver; 
 utilizing a first controller to adjust a height of a liquid level of the dissolving water in the circulation tank to adjust a feed rate of the ultrapure water to be fed to the circulation tank, said height of the liquid level being measured by a level gauge coupled to the first controller; and 
 utilizing a second controller to adjust an amount of ozone to be dissolved in the dissolving water to adjust a dissolved ozone concentration in the ozonated water, by measuring a dissolved ozone concentration in the dissolving water, before being fed to the ozone gas dissolver, calculating a feed rate of ozone gas required to increase dissolved ozone concentration to a dissolved ozone concentration required at a use point from a difference between the dissolved ozone concentration in the dissolving water before being fed to the ozone gas dissolver and the dissolved ozone concentration required at the use point to calculate the feed rate of ozone gas to be fed to the ozone gas dissolver, and adjusting a feed rate of an ozone-containing gas to the ozone gas dissolver, 
 wherein an amount of the ultrapure water fed to the circulation tank is changed in a manner that corresponds to a change in an amount of the ozonated water used at the use point. 
 
     
     
       2. The ozonated water supply method according to  claim 1 , further comprising removing particles from the ozonated water that is returned from the use point using a particle removal filter. 
     
     
       3. The ozonated water supply method according to  claim 1 , further comprising feeding ozone gas that has not been dissolved in the dissolving water using the ozone gas dissolver to the circulation tank. 
     
     
       4. The ozonated water supply method according to  claim 1 , wherein the dissolved ozone concentration in the ozonated water is adjusted by measuring a dissolved ozone concentration in the dissolving water, calculating a feed rate of ozone to be fed to the ozone gas dissolver based on the measured dissolved ozone concentration, and adjusting a feed rate of the ozone-containing gas to the ozone gas dissolver. 
     
     
       5. An ozonated water supply device comprising a circulation tank to which ultrapure water is fed, and to which ozonated water is returned from a use point, discharge-type ozone gas producer that produces ozone gas to obtain an ozone-containing gas, an oxygen gas feed pipe that feeds oxygen gas having a nitrogen gas content of 0.01 vol % or less to the ozone gas producer, an ozone gas dissolver that dissolves the ozone gas produced by the discharge-type ozone gas producer in dissolving water to obtain ozonated water, a dissolving water feed pipe that connects the circulation tank and the ozone gas dissolver, an ozone-containing gas feed pipe that connects the ozone gas producer and the ozone gas dissolver, an ozonated water feed pipe that connects the ozone gas dissolver and the use point, a return pipe that connects the use point and the circulation tank, a first controller that controls a height of a liquid level in the circulation tank, a level gauge that is coupled to the first controller and measures the height of the liquid level, a second controller that adjusts a dissolved ozone concentration in the ozonated water, and a dissolved ozone concentration adjuster that adjusts a dissolved ozone concentration in the ozonated water,
 wherein an end of the return pipe is situated in the circulation tank at a position under the liquid surface and 
 the first controller and the second controller change an amount of the ultrapure water to be fed to the circulation tank corresponding to the change in an amount of the ozonated water used at the use point. 
 
     
     
       6. The ozonated water supply device according to  claim 5 , further comprising a particle removal filter that is provided to the return pipe. 
     
     
       7. The ozonated water supply device according to  claim 5 , further comprising undissolved ozone gas feed pipe that feeds ozone gas that has not been dissolved in the dissolving water using the ozone gas dissolver to the circulation tank. 
     
     
       8. The ozonated water supply device according to  claim 5 , wherein the dissolved ozone concentration adjuster comprises a first concentration meter that measures a dissolved ozone concentration in the dissolving water, and a calculation section that calculates a feed rate of the ozone gas to be fed to the ozone gas dissolver based on the dissolved ozone concentration measured by the first concentration meter, and transmits an instruction that instructs to adjust an amount of ozone gas produced to the discharge-type ozone gas producer. 
     
     
       9. An ozonated water supply method comprising:
 feeding dissolving water contained in a circulation tank to an ozone gas dissolver at a given feed rate while feeding ultrapure water to the circulation tank, and returning ozonated water that has not been used at a use point to a position under the liquid surface in the circulation tank, dissolving ozone in the dissolving water using the ozone gas dissolver to obtain ozonated water, and feeding the ozonated water to the use point; 
 feeding oxygen gas having a nitrogen gas content of 0.01 vol % or less to a discharge-type ozone gas producer, producing ozone gas using the discharge-type ozone gas producer to obtain an ozone-containing gas, and feeding the ozone-containing gas to the ozone gas dissolver; 
 utilizing a first controller to adjust a height of a liquid level of the dissolving water in the circulation tank to adjust a feed rate of the ultrapure water to be fed to the circulation tank, said height of the liquid level being measured by a level gauge coupled to the first controller; and 
 utilizing a second controller to adjust an amount of ozone to be dissolved in the dissolving water to adjust a dissolved ozone concentration in the ozonated water, by measuring a dissolved ozone concentration in the dissolving water, before being fed to the ozone gas dissolver, calculating a feed rate of ozone gas required to increase dissolved ozone concentration to a dissolved ozone concentration required at a use point from a difference between the dissolved ozone concentration in the dissolving water before being fed to the ozone gas dissolver and the dissolved ozone concentration required at the use point to calculate the feed rate of ozone gas to be fed to the ozone gas dissolver, and adjusting a feed rate of an ozone-containing gas to the ozone gas dissolver, 
 wherein the first and second controllers adjust the feed rate of the ultrapure water fed to the circulation tank by adjusting the height of the liquid level of the dissolving water in the circulation tank, whereby an amount of the ultrapure water fed to the circulation tank is changed.